An organic EL device has the structure that a multilayer of a plurality of organic compound layers having carrier transportation and luminescence ability is sandwiched between a pair of electrodes. In such a diode structure, it is preferable to make uniform the thickness of the organic compound layer. If the thickness is not uniform, current flowing through the organic compound layer in a thickness direction becomes irregular in-plane. Decomposition of the organic compound layer is locally accelerated through exothermic, and the device lifetime is shortened.
Organic compound is soluble to organic solvent, and is deteriorated by moisture. After an organic compound layer is formed, it is therefore difficult to pattern it through photolithography. To avoid this, a shadow mask made of metal and having openings corresponding to the pixel shape and layout is used to divide an organic compound layer into pixel units. In order to allow color display, position alignment of the shadow mask is required to be performed three times corresponding to RGB. If there is an error of shadow mask position alignment, the distances between pixels become irregular and the thicknesses of organic compounds become not uniform.
The patent document 1 indicated below discloses the invention related to prevention of irregularity of distances between pixels.
FIG. 11 is a cross sectional view of an organic EL display disclosed in the patent document 1. On the surface of a substrate 100, lower electrodes 101 extending in a lateral direction in FIG. 11 are formed. A plurality of insulating films 102 extending in a direction perpendicular to the drawing sheet are formed on the surface of the substrate 100, and partition walls 103 are formed on the insulating films 102. An area of the lower electrode 101 between two adjacent partition walls 103 defines a pixel area.
The partition wall 103 is made of photosensitive resin and has an inverse taper shape broadening its width as the position becomes farther from the substrate 100. An organic compound layer 104 and an upper electrode 105 are stacked on the lower electrode 101 in each pixel area. An organic compound layer 104a and a conductive layer 105a are also formed on the partition wall 103, which are deposited when the organic compound layer 104 and upper electrode 105 are deposited.
The position of each pixel in the lateral direction in FIG. 11 is defined by the partition walls 103, and the position of each pixel in the direction perpendicular to the drawing sheet is defined by the lower electrodes 101. Therefore, the distances between pixels do not become irregular even if there is position misalignment of a shadow mask to be used when depositing an organic compound layer.
The region near the border of the organic compound layer 104 becomes thinner than the central region. If a diode is formed to the region having a thin film thickness, current is concentrated on this region. In the conventional example shown in FIG. 11, the insulating film 102 is interposed between the lower electrode 101 and the region near the border of the organic compound layer 104 to prevent current concentration on the thin region.
In this conventional example, the partition wall 103 is made of photosensitive resin. The partition wall 103 made of photosensitive resin is likely to adsorb molecules in an atmosphere. Molecules adsorbed to the partition wall 103 are gradually emitted from the partition wall 103 and affect the organic compound layer 104, accelerating deterioration of the organic compound layer 104.
If high temperature treatment is performed after the partition wall 103 is formed, molecules adsorbed to or occluded in the partition wall 103 can be emitted. However, since the partition wall 103 has an unstable inverse taper cross section, its shape is largely deformed if heat treatment is performed at a glass transition temperature or higher. Heat treatment at a sufficient high temperature is therefore impossible.
An object of this invention is to provide an organic EL display whose organic compound layers are hard to be deteriorated, and its manufacture method.